Corrugated sheet material

ABSTRACT

This invention relates to manufacturing corrugated sheet or strip from thin material. The original material has imparted thereto a series of corrugations which are coarser and wider than those finally required: at least one smaller counter-corrugation is impressed in the crest of each of the wider corrugations, and these counter-corrugations are deepened until all the corrugations resulting from this deepening are of substantially the same height. The material can be pressed together sideways to assist in the corrugating action and the invention enables the corrugations to be produced without any stretch in the material. The invention also includes a method of forming a tube which comprises taking the corrugated strip formed as above and coiling it around a mandrel in such a fashion that successive convolutions overlap preceding convolutions by approximately half the width of the strip: this produces a tube having a double wall thickness. The invention also provides apparatus for carrying out the above methods.

United States Patent [191 Siegwart CORRUGATED SHEET MATERIAL [76] Inventor: Emil Siegwart, Strasse 6, 6603 Sulzbach-Neuweiler, Germany 22 Filed: June 8,1973

21 Appl. No.: 368,216

[30] Foreign Application Priority Data June 12, 1972 Germany 2228496 [52] U.S. Cl. 72/180 [51] Int. Cl B2111 13/04 [58] Field of Search 72/180, 181

[56] References Cited UNITED STATES PATENTS 1,056,871 3/1913 White 72/180 X 3,690,137 9/1972 Cookson 72/180 Primary ExaminerMilt0n S. Mehr Attorney, Agent, or Firm-W. R. Hulbert [451 Jan. 14,1975

[57] ABSTRACT This invention relates to manufacturing corrugated sheet or strip from thin material. The original material has imparted thereto a series of corrugations which are coarser and wider than those finally required: at least one smaller counter-corrugation is impressed in the crest of each of the wider corrugations, and these counter-corrugations are deepened until all the corrugations resulting from this deepening are of substantially the same height. The material can be pressed together sideways to assist in the corrugating action and the invention enables the corrugations to be produced without any stretch in the material.

The invention also includes a method of forming a tube which comprises taking the corrugated strip formed as above and coiling it around a mandrel in such a fashion that successive convolutions overlap preceding convolutions by approximately half the width of the strip: this produces a tube having a double wall thickness. The invention also provides apparatus for carrying out the above methods.

6 Claims, 5 Drawing Figures CORRUGATED snEET MATERIAL The present invention relates to a method of and apparatus for manufacturing thin corrugated sheet or strip, in particular a strip of sheet metal for use, for example, for manufacturing a corrugated tube by coiling the strip in spiral fashion.

The danger exists, particularly when corrugating thin strips of sheet metal, such as those, for example, with a thickness of approximately 0.1 mm made of a material with high frictional characteristics that, when being radiused during corrugation, these thin sheets will split and gash since they have practically no resistance to sideways deformation. This applies particularly to brittle and hard sheet metal which can only be subjected to a small amount of stretching.

The problems mentioned are particularly prevalent in the manufacture of corrugated tubes formed by coiling corrugated strips of sheet metal in a spiral. Hitherto the procedure for this purpose has been to pass the strip which is to be corrugated and coiled spirally into a tube between a pair of revolving forming tools, namely a threaded, coarse-pitch mandrel and a nut or threaded bush with a plurality of turns which fits over. the latter, the strip receiving a multiple corrugated form like a thread between these two forming tools. In order to ensure with this type of manufacture that the strips can slide in the threaded bush and on the threaded mandrel, even where sheet metal is concerned which tends to form streaks or to scuff, the strips are covered on the inside and outside with strips of paper. Depending on the field in which the tubes are used, these strips of paper have then to be removed from the tubes, which requires an additional and laborious operation.

This known method is not only laborious, without at the same time offering absolute freedom from gashing and splitting, but also has the disadvantage that, despite its complication and expense, it is only suitable for producing tubes of a certain minimum wall-thickness. Particularly thin sheet metal cannot therefore be handled by this known method. It is, however, desirable to handle such particularly thin sheets, especially when manufacturing flexible, multilayer tubes by coiling strips in a spiral with the edges of the strips overlapping.

An object of the invention is therefore a method of and apparatus for manufacturing a thin corrugated sheet or strip, in particular a strip of sheet metal for producing a corrugated tube by coiling the strip in a spiral, in which or by means of which even brittle and hard sheet metal or relatively thin sheet metal can be corrugated in the way required substantially without gashing and tearing occurring when this is done, and without the sheet metal having to be covered on one or both sides with anti-friction layers, such as paper or the like.

This object is achieved according to the invention by firstly producing a corrugation in a flat sheet which is coarser and wider than the final corrugation required in the sheet, by then impressing, at least, one smaller counter-corrugation in the crests of these large corrugations, and by deepening these counter-corrugations until all the corrugations are equal in height. When this is done, the developed dimensions of the large corrugations are such that they correspond to the sum of the developed dimensions of the plurality of small corrugations of the required size to be formed from these large corrugations, since the method according to the invention is remarkable in that the impressing and/or deepening of the counter-corrugations takes place without the material forming the strip of sheet metal being stretched.

With the method according to the invention the procedure for forming the coarse corrugation required at the beginning may consist in that the flat sheet is firstly formed with wide and, if desired, shallow corrugations which, gradually or in increments, are made narrower and possibly deeper by closing up the corrugations by applying sideways pressure on the material. After the counter-corrugations have been impressed and deepened, all the corrugations in the sheet, once having been brought to the same height, can be compressed sideways to form the final desired shape of corrugation by further closing up of the corrugations, so that the sides of the corrugations extend substantially or almost at right angles to a tangent to the crests of the corrugations.

An apparatus which is particularly suitable for putting the method according to the invention into effect consists of a set of pairs of forming rollers positioned in succession in the direction of movement of the sheet or strip and having inter-engaging ridges and grooves situated between them, the ridges and grooves of the forming rollers first encountered in the direction of movement being of a size corresponding to the first coarse and wide corrugation to be produced in the sheet, and the forming rollers situated after them in the direction of movement having in the crests of their ridges and grooves, which are of similar size, smaller counter-grooves or counter-ridges which are intended to impress the counter-corrugations into the coarse corrugation.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings, which schematically show apparatus which is particularly suitable for putting it into effect, and in which:

FIG. II shows such apparatus in plan view,

FIG. 2 shows this apparatus from the side,

FIG. 3 shows, schematically, the various steps in the corrugating process according to the invention to be performed with this apparatus,

FIG. 4 shows, to an enlarged scale, a section through the corrugated wall of a corrugated tube produced using the apparatus of FIGS. 1 and 2, and

FIG. 5 is a partial section, to an enlarged scale, through one pair of the forming rollers associated with the apparatus shown in FIGS. 1 and 2.

Referring now to the drawings, the apparatus shown in FIGS. 1 and 2 has five mutually adjacent pairs of forming rollers I to 5 with the rollers situated one above another, the rollers being driven by a driveassembly of any desired kind, mounted in a housing 6. The strip of sheet metal 7 to be corrugated is drawn from a roll 8 and is passed through each pair of forming rollers in succession. As it is passed through the pairs of opposing forming rollers l to 5, the strip of sheet metal 7 undergoes the corrugation process described in detail below. After the strip of sheet metal has been corrugated, it is coiled onto a winding mandrel 9 which is arranged diagonally to the longitudinal direction of the strip in such a way, in the case of the embodiment shown, that the spirally wound coil of strip overlaps by half its width at any given point.

As it passes between the pairs of forming rollers l to 5, the strip is thereby deformed in five successive stages until it has the corrugation finally required. In FIG. 3 of the drawings, the stages of deformation are shown schematically underneath one another in a diagrammatic position. The straight line marked in the diagram is a schematic representation of the cross-section of the strip of sheet metal 7 immediately after it has been uncoiled from the roll 8 and prior to its first deformation. The line marked I shows the strip of sheet metal after its first deformation, which it receives from the first pair of rollers 1. In the course of this first deformation the strip of sheet metal receives wide and relatively gentle corrugations.

The second pair of rollers 2 makes the wide and gentle corrugations shown by line I narrower by closing up the corrugations by applying sideways pressure to the strip of sheet metal 7. The cross-section of the strip of sheet metal subsequent to this stage of deformation is shown in FIG. 3 by line II.

The next pair of rollers 3 make an impression in the crests of the deep and now relatively steep-flanked corrugations, which have been narrowed, in such a way that small counter-corrugations 11 are produced in the area of each of the crests of the corrugations. The strip of sheet metal now has the cross-section shown by line III in FIG. 3. The width of the counter-corrugations l1 usefully amounts to approximately a third or less than a third of the width of the deep, narrowed corrugations, while the depth of the counter-corrugations should be less than a third of the depth of the deep corrugations. These dimensions are intended to assist in making it possible to deform the strip of sheet metal 7 without stretching the material in the strip.

In the next successive pair of rollers 4, the small counter-corrugations 11 are deepened by reducing the depth of the deep corrugations formed by pair of rollers 2, so that the strip of sheet metal receives the crosssectional shape shown by line IV. The deepened counter-corrugations 11 are again deepened as the strip of sheet metal passes between the pair of forming rollers 5 to such an extend that the countercorrugations and the parts of the coarse corrugations remaining between them are of equal height. The crosssection of the strip resulting from this is shown by line V in FIG. 3.

In order to contour the strip of sheet metal 7 in the way described above, the forming rollers of the first pair 1 have at their periphery interengaging ridges with grooves situated between them which correspond in size to the coarse corrugation shown by line 1 in FIG. 3 which is to be initially produced in the sheet, while the profile of the periphery of the forming rollers of the next pair 2 is so formed with ridges and grooves that the narrowed and steeper deep corrugations shown by line II in FIG. 3 result from those corrugations being closed up sideways. The rollers in the next pairs of rollers 3, 4 and 5, are so profiled at the periphery that the counter-corrugations 11 are produced by them and are deepened in two successive stages in such a way that the cross-sections shown by lines III, IV and V in FIG. 3 are produced in the strip, in succession. Thus, in the case of forming rollers 5 of the last pair of rollers, the ridges and grooves are all of the same size and the same height.

For the sake of clarity and simplicity, the forming rollers are shown in FIGS. 1 and 2 without the requisite contouring on their periphery. In FIG. 5 however, a cross-section is shown through the peripheral region of rollers 3, which give the strip of sheet metal 7 the crosssectional shape shown schematically by line III in FIG. 3. This cross-section through the rollers shows how the two cooperating forming rollers inter-engage at their periphery so that the counter-corrugations II are impressed in the areas of the crests of the relatively deep and steep-flanked corrugations in the strip of sheet metal. I

The strip of sheet metal which has been provided with its final corrugations is next coiled onto the winding mandrel 9, the axis of rotation of which extends diagonally to the longitudinal direction of the strip, in the way described above such that the corrugations at the overlapping edges of the successive coils of the strip rest in one another as shown by the cross-section (FIG. 4 of the drawings) through the wall of the corrugated tube which is to be produced. The first convolution of the corrugated tube built up by coiling the corrugated strip of sheet metal 7 in a spiral is marked 12 in FIG. 4. The next convolution l3 overlaps this first coil 12 by approximately half its width. The edge of convolution 14, which follows convolution 13, is situated in approximately the same area as the edge of the preceding convolution 12 which overlaps convolution 13, the two convolutions 13 and 14 also overlapping one another by approximately half their width. Convolution l4 overlaps convolution 15 in the same way. Therefore, when the corrugated strip of sheet metal 7 is coiled onto the winding mandrel 9, a corrugated tube is produced which consists of two layers of corrugated sheet metal, except at its first and last coil, as a result of which the two layers of sheet metal making up the tube can be of very small thickness without prejudicing the resistance of the tube to buckling. When combined with the small thickness of sheet which may be used, the double-walled nature of the corrugated tube enables the tube to be extraordinarily flexible.

The method according to the invention described in association with the apparatus shown in the drawings may, if desired, be elaborated in respect of the number of stages of deformation. Thus, it is, for example, possible and may be useful to produce the wide or coarse shallow corrugation of the strip shown by line 1 in FIG. 3 not by one, but by two or more stages of deformation. When this is done, the flat strip of sheet metal 7 may first of all be given a less deep corrugation than that shown for the coarse corrugation line 1 in FIG. 3. These shallow corrugations can then be deepened so that the strip receives the coarse corrugation shown by line 1 in FIG. 3.

It is also possible for the sideways closing-up of the corrugated strip of sheet metal which narrows the coarse corrugation to take place in a different order from that shown in FIG. 3.

I claim:

1. A method of manufacturing a thin, corrugated sheet or strip comprising the steps of (a) taking a flat sheet of material, (b) imparting to said sheet a series of corrugations which are coarser and wider than the corrugations finally required, (c) impressing at least one smaller counter-corrugation in the crest of each of said wide corrugations and (d) deepening said countercorrugations until all the corrugations are of substantially the same height.

2. A method according to claim 1, wherein said coarse and wide corrugation formed initially is produced by first of all giving said sheet or strip broad and shallow corrugations which are deepened, gradually or by increments, by closing up and narrowing said corrugations.

3. A method according to claim 1, wherein, after said counter-corrugations have been deepened, all said corrugations, which have been reduced to the same height, are pressed together sideways by further closing up the material to form the final corrugation shape desired, so that the sides of the corrugations extend substantially or approximately at right angles to a tangent to the crests of said corrugations.

4. A method according to claim 1, wherein the deepening of said initial coarse and wide corrugations and the impressing and deepening of said countercorrugations take place without stretching said material.

5. Apparatus for forming a corrugated sheet or strip comprising a set of pairs of forming rollers, movement means for moving said sheet or strip through said rollers, said pairs being positioned in succession in the direction of movement of said sheet or strip and each pair having inter-engaging ridges and grooves situated between them, with the ridges and grooves of the forming rollers first encountered in the direction of movement corresponding in size to a first coarse or'wide corrugation to be produced in said sheet or strip, and the forming rollers situated after them in the direction of movement having smaller counter-grooves or ridges in the crests of their grooves and ridges which impress counter-currugations into said coarse corrugations, the width of said counter-ridges and counterridges and counter-grooves being approximately a third of that of the ridges and grooves on the preceding forming rollers for producing said coarse and wide corrugations, and the height of said counter-ridges and grooves being less than a third of the height of the ridges and grooves on the preceding forming rollers which form said coarse and wide corrugations.

6. Apparatus for forming a corrugated sheet or strip comprising a set of pairs of forming rollers, movement means for moving said sheet or strip through said rollers, said pairs being positioned in succession in the direction of movement of said sheet or strip and each pair having inter-engaging ridges and grooves situated between them, with the ridges and grooves of the forming rollers first encountered in the direction of movement corresponding in size to a first coarse or wide corrugation to be produced in said sheet or strip, and the forming rollers situated after them in the direction of move ment having smaller counter-grooves or ridges in the crests of their grooves and ridges which impress counter-corrugations into said coarse corrugations, said pairs of forming rollers for impressing the countercorrugations being followed by pairs of forming rollers which have ridges and grooves of the same size and height. 

1. A method of manufacturing a thin, corrugated sheet or strip comprising the steps of (a) taking a flat sheet of material, (b) imparting to said sheet a series of corrugations which are coarser and wider than the corrugations finally required, (c) impressing at least one smaller counter-corrugation in the crest of each of said wide corrugations and (d) deepening said countercorrugations until all the corrugations are of substantially the same height.
 2. A method according to claim 1, wherein said coarse and wide corrugation formed initially is produced by first of all giving said sheet or strip broad and shallow corrugations which are deepended, gradually or by increments, by closing up and narrowing said corrugations.
 3. A method according to claim 1, wherein, after said counter-corrugations have been deepened, all said corrugations, which have been reduced to the same height, are pressed together sideways by further closing up the material to form the final corrugation shape desired, so that the sides of the corrugations extend substantially or approximately at right angles to a tangent to the crests of said corrugations.
 4. A method according to claim 1, wherein the deepening of said initial coarse and wide corrugations and the impressing and deepening of said counter-corrugations take place withoUt stretching said material.
 5. Apparatus for forming a corrugated sheet or strip comprising a set of pairs of forming rollers, movement means for moving said sheet or strip through said rollers, said pairs being positioned in succession in the direction of movement of said sheet or strip and each pair having inter-engaging ridges and grooves situated between them, with the ridges and grooves of the forming rollers first encountered in the direction of movement corresponding in size to a first coarse or wide corrugation to be produced in said sheet or strip, and the forming rollers situated after them in the direction of movement having smaller counter-grooves or ridges in the crests of their grooves and ridges which impress counter-currugations into said coarse corrugations, the width of said counter-ridges and counter-ridges and counter-grooves being approximately a third of that of the ridges and grooves on the preceding forming rollers for producing said coarse and wide corrugations, and the height of said counter-ridges and grooves being less than a third of the height of the ridges and grooves on the preceding forming rollers which form said coarse and wide corrugations.
 6. Apparatus for forming a corrugated sheet or strip comprising a set of pairs of forming rollers, movement means for moving said sheet or strip through said rollers, said pairs being positioned in succession in the direction of movement of said sheet or strip and each pair having inter-engaging ridges and grooves situated between them, with the ridges and grooves of the forming rollers first encountered in the direction of movement corresponding in size to a first coarse or wide corrugation to be produced in said sheet or strip, and the forming rollers situated after them in the direction of movement having smaller counter-grooves or ridges in the crests of their grooves and ridges which impress counter-corrugations into said coarse corrugations, said pairs of forming rollers for impressing the counter-corrugations being followed by pairs of forming rollers which have ridges and grooves of the same size and height. 